[TRAFODION-1971] Avoid redundant reinitialization during bulk load
[TRAFODION-1971] Avoid redundant reinitialization during bulk load

After each flush during the preparation phase of bulk load, HFile
initialization was taking place redundantly. This imposed significant
overhead and slowed down loads.

Also removed comment regarding replacing init mechanism, in response
to review comment,

robertamarton/incubator-trafodion,mashengchen/incubator-trafodion,mashengchen/incubator-trafodion,robertamarton/incubator-trafodion,mashengchen/incubator-trafodion,mashengchen/incubator-trafodion,mashengchen/incubator-trafodion,rlugojr/incubator-trafodion,robertamarton/incubator-trafodion,robertamarton/incubator-trafodion,rlugojr/incubator-trafodion,mashengchen/incubator-trafodion,rlugojr/incubator-trafodion,robertamarton/incubator-trafodion,rlugojr/incubator-trafodion,robertamarton/incubator-trafodion,rlugojr/incubator-trafodion,rlugojr/incubator-trafodion,robertamarton/incubator-trafodion,mashengchen/incubator-trafodion,robertamarton/incubator-trafodion,rlugojr/incubator-trafodion,mashengchen/incubator-trafodion,rlugojr/incubator-trafodion,rlugojr/incubator-trafodion,robertamarton/incubator-trafodion,rlugojr/incubator-trafodion,mashengchen/incubator-trafodion,mashengchen/incubator-trafodion,robertamarton/incubator-trafodion